1. Field of the Invention
This invention relates to a ceramic multi-layer printed circuit board comprised of a combination of copper plated wiring pattern layers and insulating layers.
2. Related Art Statement
As a method of producing a ceramic multi-layer printed circuit board by alternately laminating plural wiring pattern layers and insulating layers, there have hitherto been known thick film method, thin film method, plating method and the like.
In the thick film method, the multilayer formation is carried out by forming a wiring pattern layer with Ag-Pd paste or Cu paste through a printing process and further forming an insulating layer thereon. However, the width of the wiring line formed by the printing process is critical and is 100 .mu.m at most. There is a problem that it is difficult to form fine wiring line below the above value.
In the thin film method, the wiring pattern layer is formed by sputtering process, vapor deposition process or the like and further the insulating layer is formed thereon. However, there is a problem that the equipment cost and production cost become higher.
In the plating method, the multilayer formation is carried out by forming a conductor layer through plating and further forming the insulating layer of an organic substance such as polyimide or the like thereon. Since the heat resisting temperature of polyimide is not higher than 400.degree. C., there is caused an inconvenient problem when the resulting printed circuit board is treated at a high temperature above 400.degree. C. at the subsequent step.